Bad ad practices that Google worked to stop include phishing scams to fool you into revealing personal information like passwords and account numbers, links to sites that try to trick you into installing malware, ads placed along news stories copied from legitimate news sites and violations of some Google ad privacy requirements.

There's still work to be done, though.

"Google can't keep up with the whack-a-mole," tweeted David Barnard, a developer of the free, ad-supported Weather Atlas app for iPhones. He complained specifically of ads that try to fool people into installing a new user profile that opens up a new inbox that bad actors can use to send ads, phishing attempts or other problematic emails. Google's AdMob pays the best among mobile ad networks, but he's seriously considering ditching it, he said.

Google's ad policing does operate at a massive scale. Among ad actions Google took in 2017:

Blocked 79 million ads for trying to send us to malware-infected websites.

Removed 48 million ads trying to get us to install software we don't want.